Do we need to report delayed sleep phase as a long-term health condition, or does it go away after being treated? my teen is getting ready to go to college.

Don't know: About reporting, but once better, the problem can stay away with consistent maintenance of appropriate sleep/wake schedule.

Sleep phase: I don't think this is reportable. However, after successful treatment the person must commit to staying well. This usually involves a fixed rising time and general sleep hygiene. That can be very hard for a college student. Your teen might want to talk to a dorm resident or academic advisor or college health professional on arrival at school for advice on maintaining improved sleep.